When an ancient Greek died, his soul went to the nether world:
the Hades. To reach the nether world, the souls had to cross
the river Styx, the river that separated the living from the
dead. The Styx could be crossed by ferry, whose shabby ferry-
man, advanced in age, was called Charon. The deceased's next-
of-kin would place a coin under his tongue, to pay the ferry-
man.